Upcycling of co-products and food waste, brief scientific review


The virtuous recovery (upcycling) or reuse of co-products and food waste – to produce new foods, feed, as well as ingredients for medicines and cosmetics – is the main way to minimize ‘food loss’ and halve ‘food waste’ globally by 2030 (#sdg12, target 12.3). (1)

The Department of Pharmaceutical Sciences of the University of Perugia (UniPG), under the guidance of professors Luana Perioli and Cinzia Pagano, has published and contributed to numerous studies on upcycling and reuse of ‘sidestream materials’ in agri-food supply chains. Brief review to follow.

1) Apple pomace

Apple pomace, which remains from the production of fruit juices, is rich in nutrients, micronutrients, enzymes, pectins and phytochemicals with antioxidant and antimicrobial properties worthy of attention also as natural preservatives. With promising prospects for use in food products, medicines, cosmetics and more.

The pomace they can also be used to produce natural polymers, replacing synthetic ones (i.e. carboxymethylcellulose, polyvinylpyrrolidone) which constitute sources of
microplastics whose use in the European Union is now subject to some restrictions, as we have seen, following reform of the REACH regulation. (2)

1.1) Thickeners

The combination of different methods drying (i.e. oven, freeze-drying), possible homogenization and hydroalcoholic extraction supported by ultrasound has made it possible to obtain various extracts rich in polyphenols from the apple pomace, with an excellent thickening capacity due to the ability to form a stable hydrogel.

The different treatments they influence the distribution and concentration of polyphenols and the gelatinizing properties. The best formulation was obtained with a powder (250-400 μm) dried in the oven without homogenization, since this process was found to have a negative impact on pectins and other molecules with a thickening function. (3)

1.2) Vegan mayonnaise

The same apple pomace it was included as an ingredient with a thickening function, at 2-6%, in the formula of a vegan mayonnaise. With appreciable technological results, compared with two products of the same category in both versions of traditional mayonnaise, with egg yolk, and another vegan version. (4)

The bioactive compounds with antioxidant action present in the pomace made it possible to extend the shelf life of the product, which was preferred to the others also from an organoleptic point of view in a consumer test. With the nutritional advantage, compared to classic mayonnaise, of the reduced quantity of saturated fatty acids.

Codex Alimentarius and European law, moreover, do not preclude the designation of the product as ‘vegan mayonnaise’ (5,6). And the legitimacy of the national regulations of some Member States (e.g. Belgium, Slovenia, Slovakia) which preclude this is doubtful, pending a decision from the Court of Justice of the European Union on analogous case of ‘meat sounding’.

2) Betaglucans and proteins from barley thresses

Betaglucans they are polysaccharides present in the cell walls of various foods such as barley, oats and mycoproteins, as seen. Formed by D-glucose chains in the β-1,3 position, with some bonds in the β-1,4 and β-1,6 positions depending on the species, they present various healthy properties (i.e. immunomodulation, reduction of blood cholesterol) .

The microalgae Euglena gracilis and its peculiar paramylon, which is characterized by being formed by a single linear chain (made up solely of glucose in the β-1,3 position, which crystallizes forming insoluble granules), have demonstrated the ability vitro to activate innate immune responses (7)

The barley threshers of the brewing industry, traditionally sold as raw materials for feed, can be even better exploited through the extraction of both beta-glucans and proteins recently approved by EFSA which candidate novel foods.

2.1) Bioadhesive films

An aqueous suspension consisting of different soluble and insoluble fractions of β-glucans, it was used to create a formulation for skin use in the form of biofilm, aimed at soothing and treating dermal lesions.

The use of excipients such as sorbitol and acacia gum has made it possible to improve the mechanical properties of the gel thus obtained, which can be used by casting in the preparation of films.

The property of stimulating growth of epidermal cells (keratinocytes) has also demonstrated the dual potential for use of beta-glucans, not only as an excipient but also as an active ingredient. (8)

2.2) Skin patch

A skin patch, again for the treatment of wounds, was created using β-glucans in the form of an aqueous suspension in a starch gel (corn starch) made with a 3D printer, containing glycerol and water.

The addition of alginates in the formulation it has allowed us to increase its mechanical resistance and ease of skin application for a prolonged period of time, useful for the required treatment. (9)

3) Saffron petals

The precious stigmas of saffron (Crocus sativus), are manually selected from individual flowers with high costs and minimal yields which explains their reputation as ‘red gold‘. Its petals, which represent 78% of the flowers, are instead wasted.

Saffron flowersHowever, they contain nutrients (e.g. fibre, carbohydrates, proteins, minerals, vitamins, polyunsaturated fatty acids i.e. linoleic acid) but above all secondary metabolites such as carotenoids, monoterpenes and flavonoids, which can be used in various products. (10)

3.1) Natural preservatives

Polyphenols contained in two hydroalcoholic extracts of saffron petals have demonstrated interesting bacteriostatic and bactericidal properties against various pathogenic and spoilage microorganisms which are frequent causes of contamination of food products, including various clostridia such as the dangerous Clostridium botulinumC. perfrigens e It’s hard. (11)

The two excerpts they were obtained by maceration and with the aid of an ultrasonic bath, respectively, and both contain at least 70% gallic and chlorogenic acid, which have been shown to exert an appreciable bacteriostatic and bactericidal action.

These excerpts of saffron petals represent an alternative to the use of antibiotics, as well as being able to be used as natural preservatives in various product categories (e.g. medicines, cosmetics).

3.2) Hydrogel for wounds

Three different extracts hydroalcoholics from saffron petals, prepared with 70% and 96% ethanol as solvents, were used for the preparation of a hydrogel using corn starch as a support to facilitate skin application.

The extract at 70% obtained by maceration it showed the highest antioxidant activity and ability to stimulate the regeneration of keratinocytes, thanks to the content of phenolic acids, showing excellent properties for repairing superficial damage to the epidermis.

The in vitro antimicrobial activity towards Staphylococcus epidermis is also appreciable, a native microorganism of the skin microbiota that can become pathogenic in the presence of wounds, and also develop resistance to any antibiotics used. (12)

3.3) Action on macrophages

Alcoholic extracts of saffron petals have demonstrated vitro an ability to prevent inflammation and the formation of osteoclasts, the cells responsible for the destruction of bone tissue, during the reconstruction processes carried out by osteoblasts which influence the differentiation process of macrophages (the white blood cells responsible for the phagocytosis process).

The ability to prevent differentiation of macrophages is important to prevent dysregulation of the macrophage-osteoclast axis, and determine a possible onset of problems related to inflammatory processes of bone tissue and other problems, which can result in osteoporosis, rheumatoid arthritis and osteoarthritis. (13)

4) Moringa oleifera leaf extract

The leaves of Moringa oleifera (plant known as the ‘tree of life’) are considered traditional foods. Their use in the production of foods and food supplements within the EU is therefore not subject to the prior authorization otherwise required under the Novel Food Regulation (EU) No 2015/2283.

The traditionality of use it is supported by its use in numerous preparations which have demonstrated its potential beneficial properties (e.g. antidiabetic, antibacterial, anti-carcinogenic, anti-inflammatory, cardiovascular and central nervous system) due to various substances such as polyphenols, carotenoids and glucosinolates, and by a reduced presence of anti-nutritional factors. (14)

4.1) Microparticle polymer

An extract of leaves of Moringa oleifera it has been tested as an active ingredient for the preparation of a formulation to be used for the treatment of wounds with exudate, in the form of bioadhesive polymeric microparticles obtained with the spray-drying method using chitosan as a polymer to favor the transition from sol to gel and guarantee its an immediate release of the extract quickly after skin application. (15)

The high concentration of flavonoids (e.g. quercetin in glucoside form) has made it possible to demonstrate an important antioxidant, radical scavenger and antibacterial activity, tested vitro towards Staphylococcus aureusS. epidermidisS. faecalis e S.pyogenes. The immediate release allows to accelerate the healing process, thanks also to the stimulation of the growth of keratinocytes, and adequately protect the injured area.

5) Hazelnut shells

Hazelnut shells they are the main by-product that derives from the seed extraction process, also following any preliminary roasting of the fruits. Seed shells and husks are used to produce feed, packaging, chemical reagents and energy through combustion. (16)

The substances of greatest interest contained in the peel and shells are phenolic acids, flavonoids, tannins, polysaccharides, fibers (e.g. hemicellulose) and lignin, even in toasted hazelnuts.

5.1) Antimicrobial extracts

Three extraction methods (maceration, ultrasonic bath, high power ultrasound) were tested to obtain different extracts from hazelnut shells, with various process parameters (extraction time, temperature, preliminary maceration). The extracts were characterized by a high diversity of phenolic substances, of which gallic acid was the most abundant, together with catechins and other phenolic acids. (17)

All extracts – especially those obtained after pre-maceration – have demonstrated a good ability to inhibit the growth of various microorganisms such as Bacillus cereus e Bacillus subtilis. These bacilli are involved in infection processes through the ability to produce biofilms and the direct onset of skin infections.

5.2) Polymeric skin patch

An active ingredient obtained from a water-soluble extract of hazelnut shells prepared with the casting method, it was tested in the formulation of a skin patch together with deacetylated chitosan and green clay as fillers.

Researchers have observed an interesting capacity of these extracts in stimulating the growth of keratinocytes and the skin healing process, with inhibition of the growth of S. aureus. In addition to the tensile properties useful for determining resistance during removal from packaging and skin application. (18)

6) Onion peels (Allium cepa L.)

Onion peels they are a sub-product of great interest due to the abundance of pythochemicals with an important antioxidant activity capable of increasing the shelf life of various food and non-food products. Depending on the color, substances with a coloring action can also be extracted (19)

The peel it is particularly rich in phenols, tannins and flavonoids, especially quercetin, capable of mitigating the deleterious effects of oxidative stress. The extracts, based on the technologies and methods used, can vary in terms of efficiency and in any case be valorised in the formulas of:

  • foods such as oils, baked goods, meats (to increase microbial stability),
  • active packaging, to increase the shelf life of the foods they contain.

6.1) Bioadhesive films

Polymeric films of hydrogels were made with a hydroalcoholic extract rich in flavonoids from onion skins of the red variety Rojo Duro, without the pungent odors characteristic of the bulb. Water solubility was evaluated vitro.

The tests they have demonstrated good antioxidant and radical scavenging, antibacterial and anti-inflammatory properties, safe on epidermal cells and with effective pharmacological action in the treatment of superficial wounds. (20)

6.2) Thermogel spray

The same extract was formulated with a poloxamer/chitosan polymer to obtain a thermogel spray to be used for the treatment of oral mucositis, a serious infection that can lead to painful erythematous lesions and, in the long term, difficulty in taking food or speaking fluently. With possible secondary infections of various nature. Conventional approaches (i.e. mucosal protectants, local antimicrobials, analgesia) are often not very effective.

The formulation with Rojo Duro onion extract it was effective for the treatment of mucositis, thanks to its thermosensitive and mucoadhesive properties, ensuring its permanence in the oral cavity, and the antimicrobial action active against various pathogens that promote the onset of infections. The shelf life is also guaranteed by the possibility of conservation in freeze-dried form, which maintains the properties of the thermogel for a longer period. (21)

7) Perspectives

Numerous co-products and waste of the food industry can be exploited to obtain food products and medicinal and cosmetic formulations with high added value. The studies mentioned above offer concrete evidence of the effectiveness and feasibility of circular economy applications in various food supply chains.

Opportunities to enhance the ‘sidestream materials’ are almost infinite, as shown by the shining examples of researchers from the University of Perugia. Their application can simultaneously both increase the profitability of agricultural and processing companies and reduce waste management costs.


Dario Dongo and Andrea Adelmo Della Penna


(1) Dario Dongo, Andrea Adelmo Della Penna. Food loss and waste, proposal for revision of the framework directive on waste in the EU. GIFT (Great Italian Food Trade).

(2) Kauser S. et al. (2024). Apple pome, a bioresource of functional and nutritional components with potential of utilization in different food formulations: A review. Food Chemistry Advances 4: 100598, https://doi.org/10.1016/j.focha.2023.100598

(3) Cossignani L. et al. (2023). Effect of Different Drying Treatments and Sieving on Royal Gala Apple Pomace, a Thickening Agent with Antioxidant Properties. Plants 12: 906, https://doi.org/10.3390/plants12040906

(4) Mangiapelo L. et al. (2023). Role of apple pome in the formulation of a novel healthy mayonnaise. European Food Research and Technology 249:2835–2847, https://doi.org/10.1007/s00217-023-04331-9

(5) On 8.3.76 the European Commission adopted a proposal for a directive aimed at regulating mayonnaise, sauces derived from it and other emulsified sauces for condiments, which included the use of egg yolk in emulsion as well as the definition of its characteristics . V. https://eur-lex.europa.eu/legal-content/IT/TXT/?uri=OJ:JOC_1976_054_R_0001_01

(6) Mayonnaise was regulated by the Codex Alimentarius standard CODEX STAN 168-1989. Following the recommendation of its Executive Committee (49th session), after the suspension of its review, this standard was however revoked. V. https://www.fao.org/3/X8537e/X8537e.pdf e https://www.fao.org/3/y8028e/y8028e.pdf

(7) Dario Dongo, Andrea Adelmo Della Penna. Microalgae, Euglena gracilis. Superfood with exclusive. GIFT (Great Italian Food Trade).

(8) By Michele A. et al. (2023). Formulation and characterization of sustainable bioadhesive films for wound treatment based on barley β-glucan extract obtained using the high power ultrasonic technique. International Journal of Pharmaceuticals 638: 122925, https://doi.org/10.1016/j.ijpharm.2023.122925

(9) Pérez Gutiérrez C.L. et al. (2023). The Optimization of Pressure-Assisted Microsyringe (PAM) 3D Printing Parameters for the Development of Sustainable Starch-Based Patches. Polymers 15: 3792, https://doi.org/10.3390/polym15183792

(10) Cerdá-Bernad D. et al. (2023). Underutilized Crocus Sativus L. Flowers: A Hidden Source of Sustainable High Value-Added Ingredients. Plant Foods for Human Nutrition 78:458–466, https://doi.org/10.1007/s11130-023-01065-7

(11) Primavilla S. et al. (2023). Antibacterial Activity of Crocus sativus L. Petals Extracts against Foodborne Pathogenic and Spoilage Microorganisms, with a Special Focus on Clostridia. Life 13: 60, https://doi.org/10.3390/life13010060

(12) Pagano C. et al. (2022). Starch-based sustainable hydrogel loaded with Crocus sativus petals extract: A new product for wound care. International Journal of Pharmaceuticals 625: 122067, https://doi.org/10.1016/j.ijpharm.2022.122067

(13) Orabona C. et al. (2022). Crocus sativus L. Petal Extract Inhibits Inflammation and Osteoclastogenesis in RAW 264.7 Cell Model. Pharmaceuticals 14: 1920, https://doi.org/10.3390/pharmaceutics14061290

(14) Kashyap P. et al. (2022). Recent Advances in Drumstick (Moringa oleifera) Leaves Bioactive Compounds: Composition, Health Benefits, Bioaccessibility, and Dietary Applications. Antioxidants 11 (2): 402, https://doi.org/10.3390/antiox11020402

(15) Pagano C. et al. (2020). Preparation and characterization of polymeric microparticles loaded with Moringa oleifera leaf extract for exuding wound treatment. International Journal of Pharmaceutics 587: 119700, https://doi.org/10.1016/j.ijpharm.2020.119700

(16) Zhao J. et al. (2023). Hazelnut and its by-products: A comprehensive review of nutrition, phytochemical profile, extraction, bioactivities and applications. Food Chemistry 413: 135576, https://doi.org/10.1016/j.foodchem.2023.135576

(17) By Michele A. et al. (2021). Hazelnut Shells as Source of Active Ingredients: Extracts Preparation and Characterization. Molecules 26: 6607, https://doi.org/10.3390/molecules26216607

(18) Pérez Gutíerrez C.L. et al. (2023). Polymeric Patches Based on Chitosan/Green Clay Composites and Hazelnut Shell Extract as Bio-Sustainable Medication for Wounds. Pharmaceuticals 15: 2057, https://doi.org/10.3390/pharmaceutics15082057

(19) Kumar M. et al. (2022). Onion (Allium cepa L.) peel: A review on the extraction of bioactive compounds, its antioxidant potential, and its application as a functional food ingredient. Concise Review & Hypotheses In Food Science 87 (10): 4289-4311, https://doi.org/10.1111/1750-3841.16297

(20) Pagano C. et al. (2020). Bioadhesive Polymeric Films Based on Red Onion Skins Extract for Wound Treatment: An Innovative and Eco-Friendly Formulation. Molecules 25 (2): 318, https://doi.org/10.3390/molecules25020318

(21) Loaded D. et al. (2021). Rojo Duro Red Onion Extract Loaded Spray Thermogel as a Sustainable Platform for the Treatment of Oral Mucosa Lesions. Journal of Pharmaceutical Sciences 110: 2974-2985, https://doi.org/10.1016/j.xphs.2021.04.004

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Dario Dongo, lawyer and journalist, PhD in international food law, founder of WIISE (FARE - GIFT - Food Times) and Égalité.

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Graduated in Food Technologies and Biotechnologies, qualified food technologist, he follows the research and development area. With particular regard to European research projects (in Horizon 2020, PRIMA) where the FARE division of WIISE Srl, a benefit company, participates.